In a conventional intake device for an internal combustion engine (e.g., see JP2001-248449A), a valve, which is provided for opening and closing an intake passage communicating with a combustion chamber of an internal combustion engine, is used as a valving element of a vortex flow control valve. The vortex flow control valve is configured to generate an intake vortex flow such as a tumble flow or a swirl flow in the combustion chamber of the internal combustion engine by shifting an intake air flow toward one side of the intake passage. The intake device for the internal combustion engine includes a housing, the valve, a shaft, and an electrical actuator. The housing defines the intake passage therein, and the valve is rotatably contained inside the housing. The shaft supports and fixes the valve, and the electrical actuator drives the valve in a fully-open direction or a fully-close direction through the shaft.
For example, as shown in FIG. 10A, a speed reduction mechanism of the electrical actuator includes a worm gear (not shown) fixed to an output shaft of a motor, a helical gear 101 meshing with the worm gear, a spur gear 102 located coaxially with the helical gear 101, and an output gear meshing with the spur gear 102. The helical gear 101 and the spur gear 102 are rotatably supported by an outer periphery of a support shaft fixed in the housing. Between the helical gear 101 and the spur gear 102, an impact absorbing member 103 including a rubber elastic body 113 (rubber elastomer) is disposed to rotate integrally with the helical gear 101 and the spur gear 102.
As shown in FIG. 10A, the elastic body 113 is inserted between first and second plates 111 and 112, and is vulcanized-bonded to the first and second plates 111 and 112. The elastic body 113 of the impact absorbing member 103 is twisted in use as shown in FIG. 10B. Thus, a deformation amount of the impact absorbing member 103 increases, so that an impact absorbing performance is ensured.
Therefore, a worm lock can be prevented by a twisting effect of the impact absorbing member 103 when the valve bumps into a fully-close stopper. However, in this case, the number of components and assembly man-hours are large. As a result, production cost becomes high.
Furthermore, as shown in FIG. 10A, because the elastic body 113 as rubber elastomer is vulcanized-bonded to facing surfaces of the first and second plates 111 and 112, the elastic body 113 may be separated from the facing surfaces of the first and second plates 111 and 112. Accordingly, if the elastic body 113 is separated from the facing surfaces of the first and second plates 111 and 112, connection strength between the elastic body 113 and the first plate 111 and between the elastic body 113 and the second plate 112 decreases. Thus, if an impact load operates on the first plate 111 or the second plate 112, twisting power cannot be transmitted to the elastic body 113 held between the first and second plates 111 and 112. As a result, operation reliability decreases.